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Production of High-Purity O2 Via Gas-Liquid Membrane Contactor with Oxygen Carrier Solutions

Authors: 
Pyrzynski, T., Gas Technology Institute
Meyer, H., Gas Technology Institute
Li, S., Gas Technology Institute
Zhou, S. J., Gas Technology Institute
Yu, M., University of South Carolina

Oxygen production from air has wide applications in oxygen-intensive industries, such as energy production (e.g., IGCC and oxy-combustion systems), fuels, chemicals, and other industries (e.g., steel, cement, glass, etc.). Cryogenic distillation, pressure swing adsorption, polymeric and ionic transport membrane technologies have been sued for air separation. Among these technologies, cryogenic distillation is the most mature technology for large scale and high purity (>99%) O2production. However, cryogenic distillation-based air separation is costly and energy-intensive to operate, accounting for up to 15% of the total gasification plant capital cost, and consuming over 35% of in-plant power use.

We present a novel technology to produce greater than 95% oxygen from air via a single-stage gas-liquid membrane contactor with oxygen carrier solutions as the solvent. In the process, air is sent to a membrane absorber and passes through small-diameter membrane tubes, while a lean O2 carrier solution flows counter currently on the shell side of the membrane. Unlike the other production alternatives, the air stream needs to be compressed to only a few psi and does not require heating as for the ion transport membranes or cooling for cryogenic separations. The O2 permeates through the membrane pores and is absorbed in the O2 carrier solution. The O2-rich carrier solution can be regenerated in a second membrane module (desorber) operated in a reverse process. In that case, the O2-rich carrier solution is fed to the shell side of the hollow fibers and vacuum is used to draw O2 on the bore side of hollow fibers. Compression to process conditions for integrated gasification combined cycle (IGCC), oxy-fuels, and other applications is limited to just the concentrated O2stream rather than the entire air feed stream with 79% of nitrogen. Minimizing compression and temperature changes will result in lower operating costs. 

The estimated cost including capital, operating, maintenance, and energy use for the prosopsed O2 separation technology is $19.94/ton O2, which is only about 56% of the benchmark cryogenic distillation ($35.80/ton O2). This technology has potential to produce oxygen with purity as high as 99.9% for applications in IGCC, oxy-combustion, and other advanced power generation technologies. It should offer tremendous opportunities to improve the efficiency and cost for air separation, and thus, on the overall oxygen-intensive industries.